Fuse 5 Blows When shift to reverse. V8 5.4 - F150online Forums



Fuse 5 Blows When shift to reverse. V8 5.4

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  #1  
Old 07-28-2010, 08:26 PM
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Unhappy Fuse 5 Blows When shift to reverse. V8 5.4

I have a bug that is driving me up the wall in my 2001 F-150. Whenever I shift to reverse my #5 fuse blows 95% of the time.....not all the time. This fuse is linked to the backup light, the climate control and the safety neutral switch. I've removed the bed looking for freyed or pinched wires and found nothing. I've removed the bulbs, put it in R, fuse blows. I've disconnected the backup light harness at the rear, put in R and it blows. The only time it doesn't blow is when the safety N switch is disconnected. So thought it was a bad switch. Bought a new one, put it on, put in R and the fuse blew. When the fuse blows, I have no backup lights and the A/C blows warm air. I recently had to replace the heater core and was wondering if water leaking from it got into the blend door motor and could possibly be causing the short since it's connected to the climate control selector. I'm desperate now and trying anything. Any help is appreciated. Also when I dropped the dash, to put in the core, I noticed that there's a switch on the steering column that has a plastic button on top and has three wires running to it. When the shift is in D, the button is pressed all the way in, in R it's released half way and from N thru D3 it's not engaged at all. I'm wondering if that could be the culprit. Does anyone know the name for this "switch" that I'm trying to describe? Any help is appreciated......thanks guys!
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Old 07-28-2010, 08:42 PM
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You need a road map so you can see where the backup lamp signal goes to.

See http://www.mediafire.com/file/w069l7q7xvslm65/2001 F150 Reversing Lamp Circuit.pdf
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Old 07-28-2010, 08:50 PM
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just taking a stab in the dark here, my mountaineer does the same thing, blows out the reverse lights fuse when being shifted, and from what I've read it's the od switch wires that are supposedly worn through and short out when being pulled down to drive, rangers too, but it's a different fuse. not sure if this applies, haven't had a chance to rip apart the column, but they seem to be pretty similar across ford's lines.
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Old 07-28-2010, 11:49 PM
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Quote:
Originally Posted by kp02-150 View Post
just taking a stab in the dark here, my mountaineer does the same thing, blows out the reverse lights fuse when being shifted, and from what I've read it's the od switch wires that are supposedly worn through and short out when being pulled down to drive, rangers too, but it's a different fuse. not sure if this applies, haven't had a chance to rip apart the column, but they seem to be pretty similar across ford's lines.
Doesn't apply on an F-series as the circuits are quite different. See the schematic linked to above for circuit layout.

Last edited by projectSHO89; 07-28-2010 at 11:55 PM.
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Old 07-29-2010, 10:36 AM
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Hey thanks guys for the input. project SHO89 I will download the PDF as soon as I get home and get right to tracing the wires. The admin here at work blocks things like this......guess they want us to work LOL.
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Old 07-31-2010, 01:26 AM
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since it does not blow when the digital trans range selector is disconnected, does that indicate a short somewhere between the tranny and the rear of the truck?
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Old 07-31-2010, 02:34 AM
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Just a stab in the dark here, if you have a 7 pin trailer setup might want to check the connector and wires at that point.
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Old 07-31-2010, 07:48 AM
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Originally Posted by kakings View Post
since it does not blow when the digital trans range selector is disconnected, does that indicate a short somewhere between the tranny and the rear of the truck?
Maybe, but not necessarily. See the schematic so you understand ALL the destinations of the reversing lamp signals.


Quote:
Just a stab in the dark here, if you have a 7 pin trailer setup might want to check the connector and wires at that point.
No. Read the schematic and you will see that the reversing lamp signal never goes to the 7-pin connector.
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Old 08-01-2010, 03:23 AM
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The diagram does not show the trailering lights in the reverse lamp circuit, but it does show the trailer tow reverse lamp relay. Where does that tie in if the trailer lights are not on that circuit? I will add that I didn't realize this problem until I towed my boat. After that day, it's been blowing fuses ever since. This morning, I disconnected the 7 pin connector from the main wire and it didn't blow fuses for the first half of the day. It eventually went back to doing it later this afternoon.
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Old 08-01-2010, 08:43 AM
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The reverse lamp circuit, when active, energizes a separate relay to provides a separate power feed for the trailer harness reversing lamp feed. F5 does not provide power to the trailer adapter, only to the reversing lamp relay coil in the junction box. You can pull that relay to isolate the circuits.
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Old 08-01-2010, 10:38 PM
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Unplug the DTRS and check the Black with pink strip wire for continuity to ground. Odds are it is grounded and blowing the fuse.
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Old 08-02-2010, 04:07 PM
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Checked the wires at the DTRS and they all look fine. The diagram shows that the elec. day/night mirror and central security mod and the remote anti-theft module are on the backup circuit. Where are these located so that I can take a look at the wires running to them? My first guess is under the dash, but I don't know. And just out of curiosity........why would the mirror be on the backup circuit?
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Old 08-02-2010, 07:51 PM
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Quote:
Originally Posted by kakings View Post
Checked the wires at the DTRS and they all look fine. The diagram shows that the elec. day/night mirror and central security mod and the remote anti-theft module are on the backup circuit. Where are these located so that I can take a look at the wires running to them? My first guess is under the dash, but I don't know. And just out of curiosity........why would the mirror be on the backup circuit?
Did you test the wires for a short to ground? Looking doesn't constitute a test. If you have auto dimming mirror it needs to return to daylight setting so you can see what is behind you.
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Old 08-03-2010, 12:05 AM
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I don't want to sound ignorant, but how do I go by checking for a short? The wires from the DTRS are wrapped and run to the top of the trans. I can only get to about a foot of the harness before i run out of room. I've never attempted to diagnose an electrical issue, but I'm willing to try. Hit hit me with the dumb stick.......I never paid that any attention since I almost always use my side mirrors when reversing. I found that the #5 fuse also controls the blend door. Two weeks ago, I had to drop the dash and replace the heater core. After that, the blend motor stopped working (I'm assuming due to water getting in it). Could that have anything to do with the short (although the short occured weeks before I noticed the core leaking).
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Old 08-03-2010, 09:42 AM
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The the Black with pink strip wire is what you want to use your meter and check for continuity to ground.

Turn your meter to the ohm ( or continuity setting if it has it ) and place 1 probe on the Black with pink strip wire and the other on a known good ground.

If you are using the ohm setting, the reading should be infinity ( same display as with the probes not hooked to anything ). If you get any other reading, you have a short to ground at that point.

Is this the same truck you had the bed off ?
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